Non Protein Nitrogen

Question 1

How does non-protein nitrogen arise?

Answer 1

From the breakdown of protein and nucleic acids

Question 2

What clears these NPN?

Answer 2

The kidneys, and include all substances that contain nitrogen but are not proteins or AAs

Question 3

Where are they analyzed and why?

Answer 3

In the blood to assess kidney function.

Question 4

List the NPN we are interested in

Answer 4

Urea/Blood urea Nitrogen
Creantine
Uric acid
Ammonia

Question 5

What is BUN?

Answer 5

Urea is the final product of protein breakdown. BUN measures the amount of nitrogen found as urea in the blood.

Question 6

What is BUN values used for?

Answer 6

Evaluating kidney function and perfusion

Question 7

What is BUN a primary test for?

Answer 7

Renal and hepatic functions.

Question 8

What are BUN values greatly affected by?

Answer 8

High protein diet

Dehydration

Question 9

What is azotemia?

Answer 9

This is a condition of increased BUN of >20mg/dL along with increased Cr.

Question 10

Identify the causes of azotemia.

Answer 10

• Prerenal causes: Reduced blood perfusion to kidney from shock, dehydration, heart failure
• Renal: internal to kidney
• Post renal: obstruction in urinary tract from tumor or kidney stones

Question 11

What is uremia?

Answer 11

A toxic condition in which urea is extremely elevated at 150 mg/dL accompanied by renal failure and high Cr.

Question 12

What is uremia usually accompanied by?

Answer 12

Loss of all kidney functions and systemic complications.

Question 13

Identify the complications with uremia

Answer 13

Loss of major renal functions(excretory, regulatory, synthetic)
Anemia: no EPO made
Metabolic acidosis: H+ not excreted by tubules
Renal osteodystrophy: no Vit D activation
Hyperkalemia: K+ not excreted by tubules

Question 14

What are symptoms of uremia?

Answer 14

Fatigue
Nausea
Vomiting
Uremic frost

Question 15

What is Cr normal range?

Answer 15

~0.5-1.4 mg/dL

Question 16

What is Cr?

Answer 16

Creamtine is a metabolic breakdown product of muscle.

Question 17

How is Cr concentration in blood?

Answer 17

Stable and proportional to muscle mass.

Question 18

Why is Cr better than BUN?

Answer 18

Cr is not affected by diet as BUN is

Question 19

What is Cr used to assess?

Answer 19

Glomerular filtration rate GFR

Question 20

What is GFR?

Answer 20

An estimated measurement of how much urine filtrate is produced by glomerula per minute.

Question 21

What is GFR a sensitive indicator for?

Answer 21

Kidney function

Question 22

How is Cr limited?

Answer 22

Cr is limited by increased/deceased muscle mass

Question 23

What is indicated from increased Cr and decreased GFR?

Answer 23

Poor kidney function

Question 24

What is the normal range of BUN-Cr ratio?

Answer 24

6-20

Question 25

What’s BUN-Cr ratio used for?

Answer 25

Determining causes of azotemia

Question 26

What advantage does urea have over creantinine although it is more accurate from not being affected by diet.

Answer 26

Urea is increased earlier in renal disease than Cr.

Question 27

What does high ratio of >20 BUN-Cr ratio of increased BUN and normal Cr indicate?

Answer 27

Prerenal causes of azotemia like CHf, dehydration, increased protein

Question 28

What does normal ratio of BUN-Cr with increased BUN and increased Cr levels indicated?

Answer 28

Renal disease: glomeruloneohrititis, nephrotic syndrome, uremia

Question 29

What is the formula for calculating Cr clearance?

Answer 29

(Urine Cr)(Volume Urine in mL/min) / (Plasma Cr)

Question 30

What is the correlation between Cr clearance and renal function?

Answer 30

The lower the Cr clearance, the worse renal function is.

Question 31

What is Uric acid?

Answer 31

This is a substance produced along side urea by the liver as a byproduct of the breakdown of proteins and nucleic acids.

Question 32

What nucleic acids specifically are broken down to make Uric acid?

Answer 32

Purines, AGs

Question 33

Where is UA excreted?

Answer 33

In intestines and kidneys, but 90% is reabsorbed.

Question 34

What percentage of NPN is UA?

Answer 34

~20%

Question 35

What is hyperuricemia?

Answer 35

Over production of uric acid.

Question 36

What caused hyperuricemia?

Answer 36

Overproduction of uric acid
Increased intake of purine rich foods
Increased cell breakdown, cellular injury(chemotherapy)
Undexcretion of uric acid from renal disease

Question 37

When does gout occur in re,action to hyperuricemia?

Answer 37

When levels of UA are so high that is precipitates out of solution forming urate crystals

Question 38

What is the most characteristic finding of gout?

Answer 38

Urate crystals deposit in joints = arthritis/gout

Question 39

What can happen when these urate crystals deposit naturally in urine?

Answer 39

Deposits and UA kidney stones

Question 40

What is ammonia?

Answer 40

It is a substance toxic to the brain that forms from the deanimation of amino acids.

Question 41

What does ammonia cause to the brain?

Answer 41

Hepatic encephalopathy

Question 42

Can ammonia be excreted directly through kidneys?

Answer 42

No, it has to be metabolized in the liver to form urea before being excreted as urea

Question 43

What conditions are seen with severe liver dysfunction and increased blood ammonia?

Answer 43

Hepatic encephalopathy
Reye’s syndrome
Chronic liver diseases like cancer, cirrhosis, fulminant hepatitis

Question 44

What are the two methods for analyzing Cr?

Answer 44

• Jaffee reaction: Cr + picric acid = orange red chromogen in alkaline solution.
• Enzymatic methods (increased specificity)